Apparatus And Method Of Eliminating Settling Time Delays In A Radar System

ABSTRACT

A novel and useful system and method for eliminating settling time delays in a radar system. In one embodiment, a plurality of oscillators is provided with a single transmitter. In an alternative embodiment, a plurality of transmitters is provided, each with its own oscillator. In either case, more than a single oscillator is used, whereby startup or turn on transients associated with one oscillator are allowed to settle out while another oscillator is being used. The two or more oscillators switch off and/or alternate or rotate such that oscillator settling time between chirp transmissions from the radar is substantially or completely eliminated. In a radar system having two transmitters, when the chirp propagation time window for the first transmitter is complete, the first transmitter is disconnected from the receive channel and the second transmitter is connected to the antenna and receive channel without having to wait for the second transmitter to settle since it was allowed to settle beforehand.

FIELD OF THE DISCLOSURE

The subject matter disclosed herein relates to the field of imagingradar, sonar, ultrasound, and other sensors for performing rangemeasurement via FMCW signals and/or angle measurement via digital beamforming and array processing and more particularly relates to a systemand method for eliminating settling time delays in a radar system.

BACKGROUND OF THE INVENTION

Recently, applications of radars in the automotive industry have startedto emerge. High-end automobiles already have radars that provide parkingassistance and lane departure warning to the driver. Currently, there isa growing interest in the self-driving cars and some people consider itto be the main driving force of the automotive industry in the comingyears.

Self-driving cars offer a new perspective on the application of theradar technology in automobiles. Instead of only assisting the driver,automotive radars should be capable of taking an active role in thecontrol of the vehicle. They are thus likely to become a key sensor ofthe autonomous control system of a car.

Radar is preferred over the other alternatives such as sonar or LIDAR asit is less affected by the weather conditions and can be made very smallto decrease the effect of the deployed sensor to the vehicle'saerodynamics and appearance. The Frequency Modulated Continuous Wave(FMCW) radar is a type of radar that offers more advantages compared tothe others. It ensures the range and velocity information of thesurrounded objects can be detected simultaneously. This information isvery crucial for the control system of the self-driving vehicle toprovide safe and collision-free operation.

A radar system installed in a car should be able to provide theinformation required by the control system in real-time. A basebandprocessing system is needed that is capable of providing enoughcomputing power to meet real-time system requirements. The processingsystem performs digital signal processing on the received signal toextract the useful information such as range and velocity of thesurrounded objects.

Currently, vehicles, especially cars, are increasingly equipped withtechnologies designed to assist the driver in critical situations.Besides cameras and ultrasonic sensors, car makers are turning to radaras the cost of the associated technology decreases. The attraction ofradar is that it provides fast and clear-cut measurement of the velocityand distance of multiple objects under any weather conditions. Therelevant radar signals are frequency modulated and can be analyzed withspectrum analyzers. In this manner, developers of radar components canautomatically detect, measure and display the signals in the time andfrequency domains, even up to frequencies of 500 GHz.

There is also much interest now in using radar in the realm ofautonomous vehicles which is expected to become more prevalent in thefuture. Millimeter wave automotive radar is suitable for use in theprevention of car collisions and for autonomous driving. Millimeter wavefrequencies from 77 to 81 GHz are less susceptible to the interferenceof rain, fog, snow and other weather factors, dust and noise thanultrasonic radars and laser radars. These automotive radar systemstypically comprise a high frequency radar transmitter which transmits aradar signal in a known direction. The transmitter may transmit theradar signal in either a continuous or pulse mode. These systems alsoinclude a receiver connected to the appropriate antenna system whichreceives echoes or reflections from the transmitted radar signal. Eachsuch reflection or echo represents an object struck by the transmittedradar signal.

Advanced driver assistance systems (ADAS) are systems developed toautomate/adapt/enhance vehicle systems for safety and better driving.Safety features are designed to avoid collisions and accidents byoffering technologies that alert the driver to potential problems, or toavoid collisions by implementing safeguards and taking over control ofthe vehicle. Adaptive features may automate lighting, provide adaptivecruise control, automate braking, incorporate GPS/traffic warnings,connect to smartphones, alert driver to other cars or dangers, keep thedriver in the correct lane, or show what is in blind spots.

There are many forms of ADAS available; some features are built intocars or are available as an add-on package. Also, there are aftermarketsolutions available. ADAS relies on inputs from multiple data sources,including automotive imaging, LIDAR, radar, image processing, computervision, and in-car networking. Additional inputs are possible from othersources separate from the primary vehicle platform, such as othervehicles, referred to as vehicle-to-vehicle (V2V), orvehicle-to-infrastructure system (e.g., mobile telephony or Wi-Fi datanetwork).

Advanced driver assistance systems are currently one of thefastest-growing segments in automotive electronics, with steadilyincreasing rates of adoption of industry-wide quality standards, invehicular safety systems ISO 26262, developing technology specificstandards, such as IEEE 2020 for Image Sensor quality and communicationsprotocols such as the Vehicle Information API.

In recent years many industries are moving to autonomous solutions suchas the automotive industry, deliveries etc. These autonomous platformsoperate in the environment while interacting with both the stationaryand moving objects. For this purpose, these systems require a sensorsuite which allows them to sense their surrounding in a reliable andefficient manner. For example, in order for an autonomous vehicle toplan its route on a road with other vehicle on it, the trajectoryplanner must have a 3D map of the environment with indication of movingobjects.

Visual sensors are also degraded by bad weather and poor visibility(e.g., fog, smoke, sand, rain or snow storms, etc.). They are alsolimited in estimating radial velocities. Light Detection and Rangingdevices (LIDARs) are used to measure distance to a target byilluminating that target with a laser light. These, however, areexpensive, as most have moving parts and very limited range. Thus,automotive radar is seen as an augmenting and not replacementtechnology.

In the automotive field, radar sensors are key components for comfortand safety functions, for example adaptive cruise control (ACC) orcollision mitigation systems (CMS). With an increasing number ofautomotive radar sensors operated close to each other at the same time,radar sensors may receive signals from other radar sensors. Thereception of foreign signals (interference) can lead to problems such asghost targets or a reduced signal-to-noise ratio.

Up to now, interference has not been considered as a major problembecause the percentage of vehicles equipped with radar sensors andtherefore the probability of interference was low, and the sensors wereused mainly for comfort functions. In this case it may be sufficient todetect interference and turn off the function (i.e. the entire radar)for the duration of the interference. On the contrary, safety functionsof future systems require very low failure rates. Therefore,radar-to-radar interference is a major problem in radar sensor networks,especially when several radars are concurrently operating in the samefrequency band and mutually interfering with each another. Thus, inspite of a predicted higher number of radar systems, the probability ofinterference-induced problems must be reduced.

As stated supra, a major challenge facing the application of automotiveradar to autonomous driving is the highly likely situation where severalunsynchronized radars, possibly from different vendors, operate ingeographical proximity and utilize overlapping frequency bands. Notethat the currently installed base of radars cannot be expected tosynchronize with new automotive radar sensor entrants, nor with anyglobal synchronization schemes.

Prior art digital beam forming FMCW radars are characterized by veryhigh resolutions across radial, angular and Doppler dimensions. Imagingradars are based on the well-known technology of phased arrays, whichuse a Uniformly Linearly distributed Array (ULA). It is well known thatthe far field beam pattern of a linear array architecture is obtainedusing the Fourier transform. It is also well known that rangemeasurement can be obtained by performing a Fourier transform on thede-ramped signal, generated by multiplying the conjugate of thetransmitted signal with the received signal. The radar range resolutionis determined by the RF bandwidth of the radar and is equal the speed oflight ‘c’ divided by twice the RF bandwidth.

Doppler processing is performed by performing a Fourier transform acrossthe time dimension, and its resolution is limited by the CoherentProcessing Interval (CPI). i.e. the total transmission time used forDoppler processing.

A well-known way to reduce the number of antenna elements in an array isby using a MIMO technique known as ‘virtual array’, where orthogonalwaveforms are transmitted from different antennas (usuallysimultaneously), and by means of digital processing a larger effectivearray is generated. The shape of this virtual array is the convolutionof the transmission and reception antennas.

It is also known that by means of bandpass sampling, the de-rampedsignal can be sampled with lower A/D frequencies, while preserving therange information of the targets with the ranges matching the designedbandpass filter.

In a conventional radar system, there is finite amount of time betweenchirp transmissions. This time comprises a chirp signal propagation timeas well as settling time associated with the VCO or local oscillator(LO) in the transmitter. To achieve improved resolution radar sensors,shorter duration chirps are desired. This, however, makes the settlingtime (also referred to as T_(GAP)) a larger percentage of a chirptransmission cycle. For example, consider a five-microsecond chirpduration and a two-microsecond settling time. In this case, the settlingtime comprises 40% of the chirp.

There is thus a need for a radar system that provides a solution to theabove problem. Such a system preferably minimizes T_(GAP) between chirptransmissions and maximizes the transmitted RF in the air.

SUMMARY OF THE INVENTION

The present invention a system and method for eliminating settling timedelays in a radar system. The invention is applicable to systems in thefield of imaging radar, sonar, ultrasound, and other sensors forperforming range measurement via FMCW signals and/or angle measurementvia digital beam forming and array processing.

In one embodiment, a plurality of oscillators is provided with a singletransmitter. In an alternative embodiment, a plurality of transmittersis provided, each with its own oscillator. In either case, more than asingle oscillator is used, whereby startup or turn on transientsassociated with one oscillator are allowed to settle out while anotheroscillator is being used. The two or more oscillators switch off and/oralternate or rotate such that oscillator settling time between chirptransmissions from the radar is substantially or completely eliminated.

In a radar system having two transmitters, for example, when the chirppropagation time window for the first transmitter is complete, the firsttransmitter is disconnected from the receive channel and the secondtransmitter is connected to the antenna and receive channel withouthaving to wait for the second transmitter to settle since it was allowedto settle beforehand.

There is thus provided in accordance with the invention, a method ofeliminating frequency source settling time in a radar system, the methodcomprising providing a plurality of frequency sources including at leasta first frequency source having a first required settling time and asecond frequency source having a second required settling time,alternating use of said first frequency source and said second frequencysource for transmission and reception, permitting said second frequencysource to settle while said first frequency source is in use andpermitting said first frequency source to settle while said secondfrequency source is in use, and wherein alternating use of said firstfrequency source and said second frequency source eliminates time delaysassociated with frequency source settling time in the radar system.

There is also provided in accordance with the invention, an apparatusfor eliminating frequency source settling time in a radar system,comprising one or more transmitters, one or more receivers, a pluralityof frequency sources including at least a first frequency source havinga first settling time and a second frequency source having a secondsettling time, a control circuit operative to alternately couple saidfirst frequency source and said second frequency source to said one ormore transmitters and said one or more receivers, thereby permittingsaid second frequency source to settle while said first frequency sourceis in use, and permitting said first frequency source to settle whilesaid second frequency source is in use, and wherein alternating use ofsaid first frequency source and said second frequency source eliminatestime delays associated with frequency source settling time in the radarsystem.

There is further provided in accordance with the invention, a method ofeliminating frequency source settling time in a radar system, the methodcomprising providing a plurality of frequency sources including at leasta first frequency source having a first settling time and a secondfrequency source having a second settling time, selecting said firstfrequency source and allowing settling thereof, first utilizing saidfirst frequency source for a first transmission and reception, selectingsaid second frequency source and allowing settling thereof while saidfirst frequency source is in use, upon completion of said firsttransmission and reception, turning off said first frequency source,second utilizing said second frequency source for a second transmissionand reception, selecting said first frequency source and allowingsettling thereof while said second frequency source is in use uponcompletion of said second transmission and reception, turning off saidsecond frequency source, continuing with said first utilizing wherebyalternating use of said first frequency source and said second frequencysource eliminates time delays associated with frequency source settlingtime in the radar system.

There is also provided in accordance with the invention, an apparatusfor eliminating frequency source settling time in a radar system,comprising a plurality of transmitters coupled to one or more antennas,including a first transmitter and a second transmitter, each transmitterincluding a respective frequency source having a required settling time,a plurality of receivers, a control circuit operative to alternatelycouple said first transmitter and said second transmitter to said one ormore antennas, thereby permitting the frequency source in said secondtransmitter to settle while said first transmitter is in use, andpermitting the frequency source in said first transmitter to settlewhile said second transmitter is in use, and wherein alternating use ofsaid first transmitter and said second transmitter eliminates timedelays associated with frequency source settling time in the radarsystem.

There is further provided in accordance with the invention, anautomotive radar sensor, comprising one or more transmitting antennas,one or more receiving antennas, a plurality of transceivers coupled tosaid one or more transmitting antennas and said one or more receivingantennas, said transceivers operative to generate and supplytransmitting signals to said one or more transmitting antennas andreceive signals reflected back to said one or more receiving antennas, aplurality of frequency sources coupled to said plurality of transceiversincluding at least a first frequency source having a first settling timeand a second frequency source having a second settling time, a controlcircuit operative to alternately couple said first frequency source andsaid second frequency source to said plurality of transceivers, therebypermitting said second frequency source to settle while said firstfrequency source is in use, and permitting said first frequency sourceto settle while said second frequency source is in use, and whereinalternating use of said first frequency source and said second frequencysource eliminates time delays associated with frequency source settlingtime in the automotive radar sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained in further detail in the followingexemplary embodiments and with reference to the figures, where identicalor similar elements may be partly indicated by the same or similarreference numerals, and the features of various exemplary embodimentsbeing combinable. The invention is herein described, by way of exampleonly, with reference to the accompanying drawings, wherein:

FIG. 1 is a high-level block diagram illustrating a first example radartransceiver;

FIG. 2 is a high-level block diagram illustrating a first example MIMOFMCW radar transceiver sensor;

FIG. 3 is a diagram illustrating chirp transmissions with gap periodstherebetween;

FIG. 4 is a diagram illustrating example transmitter frequency sourcesettling time;

FIG. 5 is a diagram illustrating chirp transmissions with propagationtime and frequency source settling time periods therebetween;

FIG. 6 is a high-level block diagram illustrating a second example radartransceiver incorporating multiple local oscillators (LOs);

FIG. 7 is a flow diagram illustrating a method of eliminating frequencysource settling time;

FIG. 8 is a diagram illustrating an example chirp transmission withfrequency source settling time eliminated;

FIG. 9 is a high-level block diagram illustrating a second example MIMOFMCW radar transceiver sensor incorporating multiple LOs;

FIG. 10 is a diagram illustrating an example chirp transmission withfrequency source settling time eliminated utilizing at least twotransmitters;

FIG. 11 is a high-level block diagram illustrating a third example radartransceiver incorporating multiple local oscillators (LOs);

FIGS. 12A and 12B are a high-level block diagram illustrating a fourthexample radar transceiver incorporating multiple local oscillators(LOs);

FIG. 13 is a high-level block diagram illustrating an example radarsystem incorporating a plurality of receivers and transmitters;

FIG. 14 is a flow chart illustrating an example RFBIST method of thepresent invention;

FIG. 15 is a flow chart illustrating an example TXA fault detectionmethod of the present invention;

FIG. 16 is a flow chart illustrating an example TXB fault detectionmethod of the present invention;

FIG. 17 is a flow chart illustrating an example RXA/RXB fault detectionmethod of the present invention; and

FIG. 18 is a block diagram illustrating an example digital radarprocessor IC of the present invention.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention. Itwill be understood by those skilled in the art, however, that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingfigures. Detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention which are intended to beillustrative, and not restrictive.

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings.

The figures constitute a part of this specification and includeillustrative embodiments of the present invention and illustrate variousobjects and features thereof. Further, the figures are not necessarilyto scale, some features may be exaggerated to show details of particularcomponents. In addition, any measurements, specifications and the likeshown in the figures are intended to be illustrative, and notrestrictive. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention. Further, where considered appropriate,reference numerals may be repeated among the figures to indicatecorresponding or analogous elements.

Because the illustrated embodiments of the present invention may for themost part, be implemented using electronic components and circuits knownto those skilled in the art, details will not be explained in anygreater extent than that considered necessary, for the understanding andappreciation of the underlying concepts of the present invention and inorder not to obfuscate or distract from the teachings of the presentinvention.

Any reference in the specification to a method should be applied mutatismutandis to a system capable of executing the method. Any reference inthe specification to a system should be applied mutatis mutandis to amethod that may be executed by the system.

Throughout the specification and claims, the following terms take themeanings explicitly associated herein, unless the context clearlydictates otherwise. The phrases “in one embodiment,” “in an exampleembodiment,” and “in some embodiments” as used herein do not necessarilyrefer to the same embodiment(s), though it may. Furthermore, the phrases“in another embodiment,” “in an alternative embodiment,” and “in someother embodiments” as used herein do not necessarily refer to adifferent embodiment, although it may. Thus, as described below, variousembodiments of the invention may be readily combined, without departingfrom the scope or spirit of the invention.

In addition, as used herein, the term “or” is an inclusive “or” operatorand is equivalent to the term “and/or,” unless the context clearlydictates otherwise. The term “based on” is not exclusive and allows forbeing based on additional factors not described, unless the contextclearly dictates otherwise. In addition, throughout the specification,the meaning of “a,” “an,” and “the” include plural references. Themeaning of “in” includes “in” and “on.”

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. For purposes of clarity, thesame reference numbers will be used in the drawings to identify similarelements. As used herein, the phrase at least one of A, B, and C shouldbe construed to mean a logical (A or B or C), using a non-exclusivelogical OR. It should be understood that one or more steps within amethod may be executed in different order (or concurrently) withoutaltering the principles of the present disclosure.

As used herein, the term module may refer to, be part of, or include anApplication Specific Integrated Circuit (ASIC); an electronic circuit; acombinational logic circuit; a field programmable gate array (FPGA); aprocessor (shared, dedicated, or group) that executes code; othersuitable hardware components that provide the described functionality;or a combination of some or all of the above, such as in asystem-on-chip. The term module may include memory (shared, dedicated,or group) that stores code executed by the processor.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes,and/or objects. The term shared, as used above, means that some or allcode from multiple modules may be executed using a single (shared)processor. In addition, some or all code from multiple modules may bestored by a single (shared) memory. The term group, as used above, meansthat some or all code from a single module may be executed using a groupof processors. In addition, some or all code from a single module may bestored using a group of memories.

The apparatuses and methods described herein may be implemented by oneor more computer programs executed by one or more processors. Thecomputer programs include processor-executable instructions that arestored on a non-transitory tangible computer readable medium. Thecomputer programs may also include stored data. Non-limiting examples ofthe non-transitory tangible computer readable medium are nonvolatilememory, magnetic storage, and optical storage.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, loops, circuits, and/or modules,these elements, components, loops, circuits, and/or modules should notbe limited by these terms. These terms may be only used to distinguishone element, component, loop, circuit or module from another element,component, loop, circuit or module. Terms such as “first,” “second,” andother numerical terms when used herein do not imply a sequence or orderunless clearly indicated by the context. Thus, a first element,component, loop, circuit or module discussed below could be termed asecond element, component, loop, circuit or module without departingfrom the teachings of the example implementations disclosed herein.

A high-level block diagram illustrating a first example radartransceiver is shown in FIG. 1. The radar transceiver, generallyreferenced 10, comprises a transmit path including band pass filter(BPF) 12 operative to receive a TX intermediate frequency (IF) signal26. The output of the BPF constitutes one input to mixer 14 with thesecond input signal being the local oscillator (LO) output signal 13from the single LO circuit 20. The LO circuit is operative to generateLO signal 13 utilizing phase locked loop (PLL) circuit 21 and inputreference frequency f_(R). The output of the mixer 14 is input to poweramplifier (PA) 16 and is also mixed with the received signal in thereceiver. The output of the PA is coupled to transmit antenna 18.

The receive path includes antenna 22 coupled to low noise amplifier(LNA) 23. The output of the LNA is fed to one input of the mixer 24while the output 17 of the TX mixer 14 constitutes the second input tothe mixer. The output of the mixer 24 is input to BPF 25 which generatesthe RX IF signal 27 (i.e. the beat frequency between the transmitted andreceived chirp signals.

In one embodiment, the radar comprises a time multiplexed MIMO FMCWradar. In an alternative embodiment, a full MIMO FMCW is implemented.Full MIMO radars transmit several separable signals from multipletransmit array elements simultaneously. Those signals need to beseparated at each receive channel, typically using a bank of matchedfilters. The complete virtual array is populated at once.

In time multiplexed MIMO, only one transmit (TX) array element istransmitting at a time. The transmit side is greatly simplified, andthere is no need for a bank of matched filters for each receive (RX)channel. The virtual array is progressively populated over the time ittakes to transmit from all the TX elements in the array.

Note that time multiplexed MIMO is associated with several problemsincluding coupling between Doppler and the spatial directions (azimuthand elevation). This is solved by randomizing the order in which TXarray elements transmit. Starting with an ordered transmit sequencewhich cycles over all TX elements, then repeated for the CPI duration‘REUSE’ times. The TX sequence in each repetition is randomly permuted.Each repetition uses a different permutation. Thus, it is ensured thateach TX element is transmitting the same number of times during a CPI,and that the pause between transmission, per each TX elements, is neverlonger than two periods. This is important in order to keep Dopplersidelobes low. It is marginally beneficial though not necessary tochange the permutations from one CPI to the next.

The decoupling effectiveness is largely determined by the number ofchirps in the CPI. Hence, another incentive for using short durationchirps. Doppler ambiguities occur at lower target speeds. This is solvedby randomizing the transmit (TX) sequence (as described above) and byusing relatively short chirps. A lower bound on chirp duration is thepropagation delay to the farthest target plus reasonable overlap time.In one embodiment, seven microseconds is a reasonable choice for targetslocated up to 300 meters away. Note that shorter chirps also increasethe required sampling rate as explained in more detail infra.

Regarding sensitivity, this is solved by increasing transmit power, TXand RX gain, obtaining a low noise figure and minimizing processinglosses. Reducing the sampling rate has direct and proportional impact oncomputational complexity and memory requirements. It is preferable tokeep the IF sampling rate low to keep complexity, cost and powerconsumption at reasonable levels. The required sampling rate isdetermined by the maximum IF (i.e. not RF) bandwidth of each chirp postde-ramping. The maximum IF bandwidth is determined by the chirp slope(i.e. bandwidth over duration) times the propagation delay to thefurthest target. Thus, it is preferable to keep the chirp slope low,either by low chirp bandwidth, or by long chirp duration, or acombination of both. This, however, contradicts the requirements forgood range resolution (which requires large RF bandwidth) and highDoppler ambiguity (which requires short chirps).

Frequency modulated continuous wave (FMCW) radars are radars in whichfrequency modulation is used. The theory of operation of FMCW radar isthat a continuous wave with an increasing frequency is transmitted. Sucha wave is referred to as a chirp. An example of a chirp waveform 50 isshown in FIG. 3. A high-level block diagram illustrating a first exampleMIMO FMCW radar transceiver sensor is shown in FIG. 2.

The radar transceiver sensor, generally referenced 30, comprises aplurality of M transmit circuits 38, a plurality of K receive circuits32, local oscillator (LO) 34, multiplexer 47, control circuit 49, rampor chirp generator 44, e.g., direct digital synthesizer (DDS), timedivision multiplexer (TDM) circuit block 42, and signal processing block36. In operation, the radar transceiver sensor typically communicateswith and may be controlled by a host 46. Each transmit block comprises amixer 45, power amplifier 43, and antenna 41. Each receive block 32comprises an antenna 31, low noise amplifier (LNA) 33, mixer 35,intermediate frequency (IF) block 37, and analog to digital converter(ADC) 39. In one embodiment, the radar sensor 30 comprises a separatedetection wideband receiver (not shown) dedicated to listening. Thesensor uses this receiver to detect the presence of in band interferingsignals transmitted by nearby radar sensors. The processing block usesknowledge of the detected interfering signals to formulate a response(if any) to mitigate and avoid any mutual interference.

In operation, the LO signal output of LO circuit 34 is mixed with theoutput of the TDM circuit 42 in each transmitter. The chirp signaloutput of the mixer 45 in the transmitter is input to its respective PAas well as multiplexer 47. Depending on which transmitter is active, oneof the chirp signals is distributed to the mixers 35 in the receivers 32via multiplexer 47. The select input to the multiplexer is generated bythe control block 49.

Signal processing block 36 may comprise as any suitable electronicdevice capable of processing, receiving, or transmitting data orinstructions. For example, the processing units may include one or moreof: a microprocessor, a central processing unit (CPU), anapplication-specific integrated circuit (ASIC), field programmable gatearray (FPGA), a digital signal processor (DSP), graphical processingunit (GPU), or combinations of such devices. As described herein, theterm “processor” is meant to encompass a single processor or processingunit, multiple processors, multiple processing units, or other suitablyconfigured computing element or elements.

For example, the processor may comprise one or more general purpose CPUcores and optionally one or more special purpose cores (e.g., DSP core,floating point, etc.). The one or more general purpose cores executegeneral purpose opcodes while the special purpose cores executefunctions specific to their purpose.

Attached or embedded memory comprises dynamic random access memory(DRAM) or extended data out (EDO) memory, or other types of memory suchas ROM, static RAM, flash, and non-volatile static random access memory(NVSRAM), removable memory, bubble memory, etc., or combinations of anyof the above. The memory stores electronic data that can be used by thedevice. For example, a memory can store electrical data or content suchas, for example, radar related data, audio and video files, documentsand applications, device settings and user preferences, timing andcontrol signals or data for the various modules, data structures ordatabases, and so on. The memory can be configured as any type ofmemory.

Transmitted and received signals are mixed (i.e. multiplied) to generatethe signal to be processed by the signal processing unit 36. Themultiplication process generates two signals: one with a phase equal tothe difference of the multiplied signals, and the other one with a phaseequal to the sum of the phases. The sum signal is filtered out and thedifference signal is processed by the signal processing unit. The signalprocessing unit performs all the required processing of the receiveddigital signals and controls the transmitted signal as well. Severalfunctions performed by the signal processing block include determiningrange, velocity (i.e. Doppler), elevation, azimuth performinginterference detection, mitigation and avoidance, performingsimultaneous locating and mapping (SLAM), etc.

Note that FMCW radar offers many advantages compared to the other typesof radars. These include (1) the ability to measure small ranges withhigh accuracy; (2) the ability to simultaneously measure the targetrange and its relative velocity; (3) signal processing can be performedat relatively low frequency ranges, considerably simplifying therealization of the processing circuit; (4) functioning well in varioustypes of weather and atmospheric conditions such as rain, snow,humidity, fog and dusty conditions; (5) FMCW modulation is compatiblewith solid-state transmitters, and moreover represents the best use ofoutput power available from these devices; and (6) having low weight andenergy consumption due to the absence of high circuit voltages.

When using radar signals in automotive applications, it is desired tosimultaneously determine the speed and distance of multiple objectswithin a single measurement cycle. Ordinary pulse radar cannot easilyhandle such a task since based on the timing offset between transmit andreceive signals within a cycle, only the distance can be determined. Ifspeed is also to be determined, a frequency modulated signal is used,e.g., a linear frequency modulated continuous wave (FMCW) signal. Apulse Doppler radar is also capable of measuring Doppler offsetsdirectly. The frequency offset between transmit and receive signals isalso known as the beat frequency. The beat frequency has a Dopplerfrequency component f_(D) and a delay component f_(T). The Dopplercomponent contains information about the velocity, and the delaycomponent contains information about the range. With two unknowns ofrange and velocity, two beat frequency measurements are needed todetermine the desired parameters. Immediately after the first signal, asecond signal with a linearly modified frequency is incorporated intothe measurement.

Determination of both parameters within a single measurement cycle ispossible with FM chirp sequences. Since a single chirp is very shortcompared with the total measurement cycle, each beat frequency isdetermined primarily by the delay component f_(T). In this manner, therange can be ascertained directly after each chirp. Determining thephase shift between several successive chirps within a sequence permitsthe Doppler frequency to be determined using a Fourier transformation,making it possible to calculate the speed of vehicles. Note that thespeed resolution improves as the length of the measurement cycle isincreased.

Multiple input multiple output (MIMO) radar is a type of radar whichuses multiple TX and RX antennas to transmit and receive signals. Eachtransmitting antenna in the array independently radiates a waveformsignal which is different than the signals radiated from the otherantennae. Alternatively, the signals may be identical but transmitted atnonoverlapping times. The reflected signals belonging to eachtransmitter antenna can be easily separated in the receiver antennassince either (1) orthogonal waveforms are used in the transmission, or(2) because they are received at nonoverlapping times. A virtual arrayis created that contains information from each transmitting antenna toeach receive antenna. Thus, if we have M number of transmit antennas andK number of receive antennas, we will have M·K independent transmit andreceive antenna pairs in the virtual array by using only M+K number ofphysical antennas. This characteristic of MIMO radar systems results inseveral advantages such as increased spatial resolution, increasedantenna aperture, and higher sensitivity to detect slowly movingobjects.

As stated supra, signals transmitted from different TX antennas areorthogonal. Orthogonality of the transmitted waveforms can be obtainedby using time division multiplexing (TDM), frequency divisionmultiplexing, or spatial coding. In the examples and descriptionpresented herein, TDM is used which allows only a single transmitter totransmit at each time.

A diagram depicting frequency versus time illustrating chirptransmissions with gap periods therebetween is shown in FIG. 3. Bothradar transceivers shown in FIGS. 1 and 2 are operative to periodicallytransmit chirp signals 50. The duration of the chirp is denotedT_(chirp) 52. Due to system constraints of the transmitter, a time gapT_(gap) 54 between chirps exists. This time gap comprises transmittersettling time as well as chirp signal propagation time.

A diagram illustrating example transmitter frequency source settlingtime is shown in FIG. 4. The signal 60 represents the output frequencyfouT versus time. The transients during settling time T_(setting) stemsfrom the oscillator circuit internals including VCO, PLL, or othercircuits turning on and taking a finite amount of time to reach a steadystate condition. Note that the objective of the radar system is totransmit the shortest possible chirps to optimize range and resolutionwhile maximizing the T_(chirp) to T_(gap) ratio. In this case, the onlyparameter than can be reduced is oscillator settling time, or moreprecisely, PLL settling time. The settling time T_(setting) is definedas the time is takes the PLL to lock. Transmission of the chirp is onlypossible after the PLL has achieved lock. Note also that the settlingtime is typically independent of other system parameters and must beconsidered regardless of the type of system implemented.

A frequency versus time diagram illustrating chirp transmissions withpropagation time and frequency source settling time periods therebetweenis shown in FIG. 5. The periodic chirp signals 70 having durationT_(chirp) 72 are interspaced with propagation time periods 74 andsettling time T_(setting) 76 time periods.

The goal of the present invention is to significantly reduce the gapperiod T_(gap). In other words, the objective of the radar system is tomaximize the transmitted RF in the air while minimizing the ‘notransmission’ time. The propagation time, however, cannot be changed dueto system constraints. Thus, the only way to reduce the gap time is toreduce the settling time T_(setting). In addition, the oscillatorfrequency cannot be changed or modified during propagation since it isused as the downconverter oscillator in the receiver which is typicallya homodyne receiver.

It is noted both transmitter circuits of FIGS. 1 and 2 comprise a singleoscillator circuit, e.g., PLL, LO, etc. Thus, in order to reduce andeven eliminate the settling time, in one embodiment of the invention, asecond oscillator is used. While one oscillator is used for reception ofthe reflected radar signal, the second oscillator prepares to transmit.In one embodiment, a plurality of oscillators is provided with a singletransmitter. In an alternative embodiment, a plurality of transmittersis provided, each with its own oscillator. What is critical is that morethan a single oscillator is used, whereby startup or turn on transientsassociated with one oscillator are allowed to ‘settle’ out while anotheroscillator is in use. The two or more oscillators switch off and/orrotate such that oscillator settling time between chirp transmissions issubstantially or completely eliminated.

In one embodiment, considering a plurality of transmitters (i.e. two ormore), when the chirp propagation time window is complete, the firsttransmitter is disconnected from the receive channel and the secondtransmitter is connected to the antenna and receive channel.

Note that for RF built in self-test (RFBIST) purposes, if in the eventone of the transmitter channels malfunctions, the radar system had abackup option to operate with a single transmitter but at the expense ofintroducing settling time between chirps. Thus, given a failure of atransmitter, the system can still operate but the elimination ofsettling time between chirps is sacrificed.

A high-level block diagram illustrating a second example radartransceiver incorporating multiple local oscillators (LOs) is shown inFIG. 6. The radar transceiver, generally referenced 80, comprises atransmit path including band pass filter (BPF) 82 operative to receive aTX IF signal 81. The output of the BPF constitutes one input to mixer84. The output of the mixer 84 is input to PA 86 and is mixed with thereceived signal via mixer 94. The output of the PA is coupled totransmit antenna 88.

The receive path includes antenna 90 coupled to LNA 92. The output ofthe LNA is fed to one input of the mixer 94. The other input is thechirp signal output of mixer 84. The output of the mixer 94 is input toBPF 96 which generates the RX IF signal 97.

In one embodiment, the system comprises dual local oscillators (LOs),namely LO1 100 and LO2 102, each incorporating its own PLL circuit 101.The oscillator signals generated by the two LO circuits are input to anRF switch 98 which is controlled by LO control block 104. The output ofthe RF switch constitutes the second input to mixer 84. The LO circuits100, 102 are operative to generate separate LO signals utilizingindependent PLL circuits 21 and input reference frequencies f_(R).

In operation, the LO circuits alternate as described in more detailbelow. A flow diagram illustrating a method of eliminating frequencysource settling time is shown in FIG. 7. At least two intendentfrequency sources LO1 and LO2 are provided (step 260). LO1 is turned onand allowed to settle (step 262). Once settled, LO1 is then used fortransmit and receive (step 264). While LO1 is in use, LO2 is turned onand allowed to settle (step 266). Note that LO2 is turned on earlyenough that it will settle before LO1 is to be turned off.

Once LO1 transmission and reception is complete (step 268), LO1 isturned off (step 270). LO2 is then used for transmit and receive (step272). While LO2 is in use, LO1 is turned on and allowed to settle (step274). Once LO2 transmission and reception are complete (step 276), LO2is turned off (step 278) and the method repeats.

A diagram illustrating frequency versus time for an example chirptransmission with frequency source settling time eliminated is shown inFIG. 8. In one example embodiment, consider a two transmitter radarsystem. LO1 is turned is used to generate and transmit chirp 110 duringT_(chirp) 112. A propagation time period 114 follows the end of thetransmission of the chirp whereby the receiver listens for echo returnsignals. At the end of the propagation time 114, LO1 is turned off. LO1is on, however, for the entire chirp transmission duration as well asthe propagation time period 114 for a combined time period 116. LO1 mustturn on some time before the transmitter starts transmission of thechirp 110. This is to allow for settling time. The LO1 signal is used inthe homodyne receiver during the chirp time period and the propagationtime period.

Once the LO1 propagation time period is complete, LO2 is used togenerate and transmit chirp 118 during T_(chirp) 120. A propagation timeperiod 124 follows the end of the transmission of the chirp whereby thereceiver listens for echo return signals. At the end of the propagationtime 124, LO2 is turned off. LO2 is on, however, for the entire chirptransmission duration as well as the propagation time period 124 for acombined time period 122. LO2 must turn on some time before thetransmitter starts transmission of the chirp 118. This is to allow forsettling time. The LO2 signal is used in the homodyne receiver duringthe chirp time period and the propagation time period.

In this fashion, the two local oscillators (i.e. transmitters) alternateturning on and off at appropriate times so as to eliminate any settlingtime that would normally be present (see FIG. 5) absent two or moretransmitters or a single transmitter with multiple local oscillators.

A high-level block diagram illustrating a second example MIMO FMCW radartransceiver sensor incorporating multiple LOs is shown in FIG. 9. Theradar transceiver sensor, generally referenced 130, comprises aplurality of M transmit circuits 138, a plurality of K receive circuits132, ramp or chirp generator 144, e.g., direct digital synthesizer(DDS), TDM circuit block 142, multiplexer 147, control circuit 149, andsignal processing block 136. In operation, the radar transceiver sensortypically communicates with and may be controlled by a host 146. Eachtransmit block comprises a mixer 145, local oscillator 134, poweramplifier 143, and antenna 141. Each receive block 132 comprises anantenna 131, low noise amplifier (LNA) 133, mixer 135, intermediatefrequency (IF) block 137, and analog to digital converter (ADC) 139. Inone embodiment, the radar sensor 130 comprises a separate detectionwideband receiver (not shown) dedicated to listening. The sensor usesthis receiver to detect the presence of in band interfering signalstransmitted by nearby radar sensors. The processing block uses knowledgeof the detected interfering signals to formulate a response (if any) tomitigate and avoid any mutual interference.

In one embodiment, each of the M transmitters comprises a separate localoscillator circuit 134, each LO circuit incorporating an individual PLL140. Thus, transmitter 1 comprises LO1 which is operative to generate anoscillator signal f_(LO1), transmitter 2 comprises LO2 which isoperative to generate an oscillator signal f_(LO2), and so on throughtransmitter M which comprises LOM which is operative to generate anoscillator signal f_(LOM). Control of the local oscillator circuits inthe M transmitters is provided by the control block 149. The controlcircuit is operative to configure, inter alia, the oscillator frequencyof each LO circuit 134. The chirp signals output of each of the mixercircuits 145 are input to multiplexer 147 which is operative to selectone of the TX output signals for mixing with the receive signal in eachreceiver.

On the receive side, the M output chirp signals are input to amultiplexer 147 whose SEL line 148 is controlled by the control block149 or other control circuit. Depending on the local oscillator andtransmitter currently selected, the multiplexer is appropriatelyconfigured to pass the output chirp signal generated by the operativetransmitter to mixers 135 in the K receivers.

Thus, the radar transceiver is operative to provide a separate LO signalto the M transmitters where the LO signal generated by each transmitteris independent and distinct from that of all other transmitters.

Note that in this embodiment, the chirp signal is generated by the chirpgenerator 144 and upconverted via mixing with the PLL signal. It isappreciated by one skilled in the art that alternatively in this andother embodiments disclosed herein the PLL itself can be directlymodulated to generate the chirp signal without departing from the scopeof the invention.

A diagram illustrating an example chirp transmission with frequencysource settling time eliminated utilizing at least two transmitters isshown in FIG. 10. In this example, two transmitters, i.e. TX1 and TX2,alternate transmissions. Thus, while one transmitter is transmitting,the other is settling and preparing to transmit.

Consider TX1 transmitting chirp 150 during T_(chirp) 152. Thetransmitter turns off and the receiver continues listening for echoreturns during propagation time 154. At some point in time before theend of the propagation time period 154, TX2 oscillator (i.e. LO2) turnson and is allowed to settle during settling time period 156. Once theTX1 propagation time interval 154 is complete, TX2 immediately turns onand begins transmitting chirp 158 during T_(chirp) 157. The LO2oscillator signal continues to be used in the receiver until thepropagation time interval 160 is complete.

At some point in time before the end of the propagation time period 160,TX1 oscillator (i.e. LO1) turns on and is allowed to settle duringsettling time period 162. Once the TX2 propagation time interval 160 iscomplete, TX1 immediately turns on and begins transmitting chirp 164during T_(chirp) 163. The LO1 oscillator signal continues to be used inthe receiver until the propagation time interval 166 is complete. Atthat time, LO2 has settled and TX2 begins transmitting chirp 170.

Thus, the use of at least two transmitters and corresponding localoscillators, e.g., TX1, TX2 and LO1, LO2, permits the elimination of thesettling time that normally would be present between chirps in a systemhaving a single LO and transmitter.

A high-level block diagram illustrating a third example radartransceiver incorporating multiple local oscillators (LOs) is shown inFIG. 11. The radar transceiver sensor, generally referenced 180,comprises a plurality of M transmit circuits 188, a plurality of Kreceive circuits 182, ramp or chirp generator 194, e.g., direct digitalsynthesizer (DDS), TDM circuit block 192, control circuit 200, andsignal processing block 186. In operation, the radar transceiver sensortypically communicates with and may be controlled by a host 196. Eachtransmit block comprises a mixer 195, power amplifier 193, and antenna191. Each receive block 182 comprises an antenna 181, low noiseamplifier (LNA) 183, mixer 185, intermediate frequency (IF) block 187,and analog to digital converter (ADC) 189. In one embodiment, the radarsensor 180 comprises a separate detection wideband receiver (not shown)dedicated to listening. The sensor uses this receiver to detect thepresence of in band interfering signals transmitted by nearby radarsensors. The processing block uses knowledge of the detected interferingsignals to formulate a response (if any) to mitigate and avoid anymutual interference.

In one embodiment, the radar transceiver comprises K local oscillatorcircuits 202, with each LO circuit incorporating an individual PLL 201.Local oscillator LO1 is operative to generate an oscillator signalf_(LO1), local oscillator LO2 is operative to generate an oscillatorsignal f_(LO2), and so on through local oscillator LOJ which isoperative to generate oscillator signal f_(LOJ). Control of the J localoscillator circuits is provided by the control block 200. The controlcircuit is operative to configure, inter alia, the oscillator frequencyof each LO circuit 202. The oscillator signals f_(LO1) through f_(LOJ)output of the J local oscillator circuits, respectively, are input to amultiplexer 206 whose SEL1 line 208 is provided by the control block 200or other suitable control circuit.

In this embodiment, all M transmitters are operative to use the samelocal oscillator signal selected by the control block. While one of theLO signals is being used, another LO circuit is turned on and allowed tosettle. Once the current propagation interval is complete, the controlblock is operative to configure the multiplexer 206 to select the nextLO signal to be fed to the transmitters. Thus, the radar transceiver isoperative to provide a common LO signal to the M transmitters.

The chirp signals output of the mixer 195 in each transmitter is inputto a multiplexer 205 whose output is input to the mixer 185 in each ofthe K receivers where it is mixed with the received signal output fromthe LNA. The control circuit 200 is operative to generate the selectline SEL2 that is used to select the chirp signal from one of the Mtransmitters.

A high-level block diagram illustrating a fourth example radartransceiver incorporating multiple local oscillators (LOs) is shown inFIGS. 12A and 12B. The radar transceiver, generally referenced 210,comprises a plurality of transmitter integrated circuits (ICs, chips,devices, etc.) 216, a plurality of receiver chips 240, chirpgenerator/DDS 214, all coupled to signal processing block 212. In oneembodiment, the example transceiver 210 is suitable for use in a FMCWMIMO radar. The radar transceiver 210 is operative to perform the methodof the present invention as described in connection with FIG. 7 supra.

Each transmitter chip, TX1, TX2, comprises a plurality of transmitterchannels, PLL 230 adapted to receive a reference PLL clock 223, localoscillator (i.e. frequency source) 232 whose output signal f_(O1) isoptionally coupled to a frequency multiplier (not shown), e.g., X1, X2,X4, X8, etc., TDM block 218, a plurality of mixers 220 adapted toreceive the LO signal, a plurality of power amplifiers 222, and controlregister 217. The TX2 chip is operative to generate a separate LO signalf_(O2). The outputs of the PAs of both TX1 and TX2 are input to an RFswitch 224 which steers RF signals to the plurality of transmit antennas226 in accordance with a control signal. The chirp signals output of themixers 220 in the transmitters 216 (i.e. TX1 and TX2) are input tomultiplexer 234 whose select control is generated by control block 259.The output f_(O) 221 is mixed with the received signal in the receivers.

The control registers 217 are operative to configure and control theproperties and parameters of the circuits contained on the transmitterchips. For example, parameters such as carrier frequency, chirpduration, frequency gradient of the chirp, etc.

Each receiver chip, RX1, RX2, comprises a plurality of channels, aplurality of LNAs 244 adapted to receive input signals from antennas242, mixers 246, IF blocs 248 and ADCs 250. Each receiver chip alsooptionally comprises a frequency multiplier circuit (not shown), e.g.,X1, X2, X4, X8, etc., adapted to receive LO signal f_(O) 221 beforeinput to the mixers 246.

In one embodiment, each receiver chip comprises a system clock generatorcircuit 252 operative to generate PLL reference clock signal 223 whichis input to local oscillator circuits 232 in the transmitter chips. Thereceiver chip also comprises a control register 241. The controlregisters 241 are operative to configure and control the properties andparameters of the circuits contained on the receiver chips, such as PLLclock frequency 223, etc.

In one embodiment, the transceiver 210 is used in an automotive radarFMCW MIMO based system. Such a system requires a plurality oftransmitter and receiver channels to achieve desired range, azimuth,elevation and velocity. The higher the number of channels, the betterthe resolution performance. In the example shown herein, the systemcomprises two receiver chips and two transmitter chips. Each TX chipcomprises a plurality of transmitter channels and each RX chip comprisesa plurality of receiver channels. It is appreciated, however, that thesystem can include more than two receiver and/or transmitter chips. EachTX and RX chip is operable as part of a larger system adapted to achievemaximum system performance. In one embodiment, in a complete systemthere is a single control channel that may be integrated in a RX chip.The control channel is operative to configure the entire setup of bothTX and RX devices. When the control channel is integrated in a RXdevice, one of the RX devices functions as a master device and all otherRX devices are slave devices.

A high-level block diagram illustrating an example radar systemincorporating a plurality of receivers and transmitters is shown in FIG.13. The radar system, generally referenced 280, comprises a digitalradar processor (DRP) for performing, inter alia, signal processingfunctions, a plurality N of transmitter devices TX1 to TXN 284, eachcoupled to an antenna 288, a plurality M of receiver devices RX1 to RXN286, each coupled to an antenna 290. TX data lines 292 connect the DRPto the transmitter devices, RX lines 294 connect the receiver devices tothe DRP, and control signal 296 are provided by the DRP to each of thetransmitter and receiver devices, 284, 286, respectively. Note that Nand M may be any positive integer greater than one.

A flow chart illustrating an example RFBIST method of the presentinvention is shown in FIG. 14. In one embodiment, the requirements ofthe ISO 26262 safety standard is met by testing each transmitter deviceand receiver device at least ten times per second. The RFBIST method,however, operative on pairs of transmitters and receivers at a time.Thus, to meet the requirements of the standard, the RFBIST method isexecuted often enough such that every transmitter and receiver is testedat least ten times per second.

First, a pair of transmitters and a pair of receivers are selected for aparticular test (step 300). The selected transmitter and receivers aredesignated TXA, TXB, RXA, and RXB (step 302). The TXA transmitter faultdetection test is then performed (step 304), followed by the TXBtransmitter fault detection test (step 306). The combined RXA/RXBreceiver fault detection test is then performed (step 308). These testsare repeated a sufficient number of times and often enough such that allN transmitter devices and M receiver devices are tested to meet therequirements of the relevant safety standard, e.g., ten times per secondfor the ISO 26262 safety standard.

Note that these tests are preferably performed with minimal impact onthe regular operation of the radar system. In other words, it isdesirable that the processing and latency impact on the radar forperforming the RFBIST mechanism be zero or minimal at most.

A flow chart illustrating an example TXA fault detection method of thepresent invention is shown in FIG. 15. In one embodiment, a transmitterfault is detected by using a second transmitter to verify the validityof the transmitted signal. First, a signal is transmitted from TXA (step320). If both receivers RXA and RXB detect valid signals (step 322),then TXA is declared operational and no fault detected (step 324). If,however, receivers RXA and RXB do not detect a valid signal (step 322),then it may be that transmitter TXA is faulty. To verify this, a signalis transmitted from the other transmitter TXB (step 326).

If both receivers RXA and RXB detect valid signals (step 328), then afault in the first transmitter TXA is declared (step 332). If, however,both receivers RXA and RXB do not detect valid signals (step 328), thenit is possible that TXB is faulty and should be checked (step 330). Itis also possible that both receivers RXA and RXB are also faulty but thelikelihood is relatively low. Both receivers are tested independently inany event.

Note that the method of detecting valid signals may comprise anysuitable technique for determining whether the signal received at areceiver device is acceptable. For example, the signal to be analyzedmay be taken from the output of the ADC before any FFT processing (e.g.,range FFT) is performed on the signal by the radar processing unit (RPU)404 (FIG. 18). Any desired characteristics of the radar signal may beused to determine signal validity. In one embodiment, the radartransceiver is calibrated at the time of manufacture such as in ananechoic chamber. During the calibration process, one or more metrics orcharacteristics related to a reference radar signal are determined andstored in the processor IC or otherwise made available for futurereference by the radar system. Examples of characteristics includeexpected power density distribution measurements, power histograms,frequency, frequency bandwidth, average frequency, etc. In oneembodiment, during the factory calibration process, the entire systemelectrical response (including the antenna and RF paths) is recorded.Note that preferably, the calibration is performed in a controlledenvironment (e.g., RF isolated anechoic chamber). As part of calibrationprocess, the data is recorded and extracted to optimize the settings ofthe radar. The data recorded can be used to check the correlation(cross-correlation) between channels during operation of the radar.

When a receiver receives a signal from a transmitter, one or morecharacteristics of the signal are compared to those stored in memory,e.g., correlated. If the correlation results are close enough, i.e. theyexceed a static or dynamic threshold (and may be set by the user), thereceived signal is declared valid. For example, power histograms can begenerated after one or more FFTs per TX-RX pair (i.e. part of the radarprocessing).

Note that when active, the radar is constantly performing transmit andreceive actions. The RFBIST operations and processing are preferablyperformed in the background without any performance degradation to themain operation of the radar. The difference between adjacent receivechannels is the distance the transmit signal travels and variance in thereflection coefficient from the target. The received signal can havesignal properties which are similar to other channels with differencescaused by the reflection coefficient and traveling distance. In regularoperation of the radar, it is expected that properties like receivedaverage power and power distribution of the signal will have goodcorrelation from one receiver to another. This fact can be used toidentify faulty channels.

In addition, the radar chirp frequency can be monitored in real time bythe receiver devices. In one embodiment, the frequency of the LO signalat the receiver during the frequency ramp can be estimated and comparedin real time to the expected frequency ramp. This eliminates the needfor lock detection at the transmitter.

For example, when an abnormal power distribution is received anddetected, the system alerts a higher-level hierarchy that the system isimpaired. The system, however, can recover by masking (i.e. ignoring)the channels that are defective, i.e. calculating and determining whichparts of the antenna array and TX/RX circuits have been found faulty andnot considering them in generating the output radar image data.Moreover, in one embodiment, the system powers down any channels in thearray that have been found faulty in order to save power. Note that thehigher-level is operative to manage the sensors and fuse the data toactuate physical operation of the vehicle (i.e. accelerate, brake, stop,turn, etc.).

A flow chart illustrating an example TXB fault detection method of thepresent invention is shown in FIG. 16. Similar to the method to detect aTXA fault, a second transmitter is used to verify the validity of thetransmitted signal. First, a signal is transmitted from TXB (step 340).If both receivers RXA and RXB detect valid signals (step 342), then TXBis declared operational and no fault detected (step 344). If, however,receivers RXA and RXB do not detect a valid signal (step 342), then itmay be that transmitter TXB is faulty. To verify this, a signal istransmitted from the other transmitter TXA (step 346).

If both receivers RXA and RXB detect valid signals (step 348), then afault in the second transmitter TXB is declared (step 352). If, however,both receivers RXA and RXB do not detect valid signals (step 348), thenit is possible that TXA is faulty and should be checked (step 350). Itis also possible that both receivers RXA and RXB are also faulty but thelikelihood is relatively low. Both receivers are tested independently inany event.

A flow chart illustrating an example RXA/RXB fault detection method ofthe present invention is shown in FIG. 17. In this method, bothreceivers RXA and RXB are tested and a fault in either can be detected.First, a signal is transmitted from transmitter TXA (step 360). Thesignal received by receiver RXA is then correlated with the signalreceived by receiver RXB (step 362). If the correlation results exceed athreshold, i.e. the two received signals match sufficiently (step 364),then both receivers RXA and RXB are declared operational and no fault isdetected (step 365).

If, however, the correlation between the two received signal does notexceed the threshold (step 364), then a signal from the othertransmitter TXB is transmitted (step 366). At this point, each receiverRXA and RXB has received two signals, one from transmitter TXA and theother from transmitter TXB. The two transmit signals received at eachreceiver are correlated. Thus, the signals received on receiver RXA fromtransmitters TXA and TXB are correlated (step 368), as well as thesignals received on receiver RXB from transmitters TXA and TXB arecorrelated (step 376).

If the TXA and TXB signals received at receiver RXA correlate with eachother (i.e. the correlation results exceed a predetermined threshold)(step 370), then RXA is declared operational and no RXA fault isdetected (step 372). If the TXA and TXB signals received at receiver RXAdo not correlate with each other (i.e. the correlation results do notexceed a predetermined threshold) (step 370), then a fault in receiverRXB is declared (step 374).

If the TXA and TXB signals received at receiver RXB correlate with eachother (i.e. the correlation results exceed a predetermined threshold)(step 378), then RXB is declared operational and no RXB fault isdetected (step 382). If the TXA and TXB signals received at receiver RXBdo not correlate with each other (i.e. the correlation results do notexceed a predetermined threshold) (step 378), then a fault in receiverRXA is declared (step 380).

A block diagram illustrating an example digital radar processor IC ofthe present invention is shown in FIG. 18. The radar processor IC,generally referenced 390, comprises several chip service functions 392including temperature sensor circuit 396, watchdog timers 398, power onreset (POR) circuit 400, etc., PLL system 394 including power domaincircuit 402, radar processing unit (RPU) 404 including parallel FFTengine 406, data analyzer circuit 408 and direct memory access (DMA)circuit 410, CPU block 412 including TX/RX control block 414, safetycore block 418, and L1 and L2 cache memory circuit 424, memory system426 and interface (I/F) circuit 428.

The TX/RX control circuit 414 incorporates settling time control block416 which implements the mechanism of the present invention foreliminating frequency source settling time, described in detail supra.The safety core block 418 includes system watchdog timer circuitry 420and RFBIST circuit adapted to implement the RFBIST mechanism of thepresent invention described in detail supra. The I/F circuit includesinterfaces for radar output data 430, TX control 432, RX control 434,external memory 436, and RF clock 438.

Note that the digital radar processor circuit 390 can be implemented onmonolithic silicon or across several integrated circuits, depending onthe particular implementation. Similarly, the transmitter and receivercircuits can be implemented on a single IC or across several ICsdepending on the particular implementation.

Any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality may be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermediary components. Likewise, any two componentsso associated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundariesbetween the above described operations merely illustrative. The multipleoperations may be combined into a single operation, a single operationmay be distributed in additional operations and operations may beexecuted at least partially overlapping in time. Moreover, alternativeembodiments may include multiple instances of a particular operation,and the order of operations may be altered in various other embodiments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim. The use of introductory phrases suchas “at least one” and “one or more” in the claims should not beconstrued to imply that the introduction of another claim element by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim element to inventions containing only one suchelement, even when the same claim includes the introductory phrases “oneor more” or “at least one” and indefinite articles such as “a” or “an.”The same holds true for the use of definite articles. Unless statedotherwise, terms such as “first,” “second,” etc. are used to arbitrarilydistinguish between the elements such terms describe. Thus, these termsare not necessarily intended to indicate temporal or otherprioritization of such elements. The mere fact that certain measures arerecited in mutually different claims does not indicate that acombination of these measures cannot be used to advantage.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description but is not intended to be exhaustive orlimited to the invention in the form disclosed. As numerousmodifications and changes will readily occur to those skilled in theart, it is intended that the invention not be limited to the limitednumber of embodiments described herein. Accordingly, it will beappreciated that all suitable variations, modifications and equivalentsmay be resorted to, falling within the spirit and scope of the presentinvention. The embodiments were chosen and described in order to bestexplain the principles of the invention and the practical application,and to enable others of ordinary skill in the art to understand theinvention for various embodiments with various modifications as aresuited to the particular use contemplated.

1. A method of eliminating frequency source settling time in a radarsystem, the method comprising: providing a plurality of frequencysources including at least a first frequency source having a firstrequired settling time and a second frequency source having a secondrequired settling time; alternating use of said first frequency sourceand said second frequency source for transmission and reception;permitting said second frequency source to settle while said firstfrequency source is in use and permitting said first frequency source tosettle while said second frequency source is in use; and whereinalternating use of said first frequency source and said second frequencysource eliminates time delays associated with frequency source settlingtime in the radar system.
 2. The method according to claim 1, whereinalternating use of said first frequency source and said second frequencysource for transmission and reception comprises: connecting said firstfrequency source to one or more transmitters and one or more receiverswhile permitting said second frequency source to settle; and connectingsaid second frequency source to said one or more transmitters and saidone or more receivers while permitting said first frequency source tosettle.
 3. The method according to claim 2, wherein alternating use ofsaid first frequency source and said second frequency source fortransmission and reception comprises: disconnecting said first frequencysource from said one or more transmitters and said one or more receiverswhen transmission and reception using said first frequency source iscomplete; and disconnecting said second frequency source from said oneor more transmitters and said one or more receivers when transmissionand reception using said second frequency source is complete.
 4. Themethod according to claim 1, wherein said first frequency sourcecomprises a first phase locked loop (PLL) circuit and said secondfrequency source comprises a second PLL circuit.
 5. An apparatus foreliminating frequency source settling time in a radar system,comprising: one or more transmitters; one or more receivers; a pluralityof frequency sources including at least a first frequency source havinga first settling time and a second frequency source having a secondsettling time; a control circuit operative to alternately couple saidfirst frequency source and said second frequency source to said one ormore transmitters and said one or more receivers, thereby permittingsaid second frequency source to settle while said first frequency sourceis in use, and permitting said first frequency source to settle whilesaid second frequency source is in use; and wherein alternating use ofsaid first frequency source and said second frequency source eliminatestime delays associated with frequency source settling time in the radarsystem.
 6. The apparatus according to claim 5, wherein said firstfrequency source comprises a first phase locked loop (PLL) circuit andsaid second frequency source comprises a second PLL circuit.
 7. Theapparatus according to claim 5, wherein said control circuit isoperative to disconnect said first frequency source from said one ormore transmitters and said one or more receivers when transmission andreception using said first frequency source is complete.
 8. Theapparatus according to claim 5, wherein said control circuit isoperative to disconnect said second frequency source from said one ormore transmitters and said one or more receivers when transmission andreception using said second frequency source is complete.
 9. A method ofeliminating frequency source settling time in a radar system, the methodcomprising: providing a plurality of frequency sources including atleast a first frequency source having a first settling time and a secondfrequency source having a second settling time; selecting said firstfrequency source and allowing settling thereof; first utilizing saidfirst frequency source for a first transmission and reception; selectingsaid second frequency source and allowing settling thereof while saidfirst frequency source is in use; upon completion of said firsttransmission and reception, turning off said first frequency source;second utilizing said second frequency source for a second transmissionand reception; selecting said first frequency source and allowingsettling thereof while said second frequency source is in use; uponcompletion of said second transmission and reception, turning off saidsecond frequency source; continuing with said first utilizing wherebyalternating use of said first frequency source and said second frequencysource eliminates time delays associated with frequency source settlingtime in the radar system.
 10. The method according to claim 9, whereinsaid first utilizing comprises connecting said first frequency source toone or more transmitters and one or more receivers while permitting saidsecond frequency source to settle.
 11. The method according to claim 9,wherein said second utilizing comprises connecting said second frequencysource to one or more transmitters and one or more receivers whilepermitting said first frequency source to settle.
 12. An apparatus foreliminating frequency source settling time in a radar system,comprising: a plurality of transmitters coupled to one or more antennas,including a first transmitter and a second transmitter, each transmitterincluding a respective frequency source having a required settling time;a plurality of receivers; a control circuit operative to alternatelycouple said first transmitter and said second transmitter to said one ormore antennas, thereby permitting the frequency source in said secondtransmitter to settle while said first transmitter is in use, andpermitting the frequency source in said first transmitter to settlewhile said second transmitter is in use; and wherein alternating use ofsaid first transmitter and said second transmitter eliminates timedelays associated with frequency source settling time in the radarsystem.
 13. The apparatus according to claim 12, wherein said firstfrequency source comprises a first phase locked loop (PLL) circuit andsaid second frequency source comprises a second PLL circuit.
 14. Theapparatus according to claim 12, wherein said control circuit isoperative to turn said first frequency source off when transmission andreception using said first frequency source is complete.
 15. Theapparatus according to claim 12, wherein said control circuit isoperative to turn said second frequency source off when transmission andreception using said second frequency source is complete.
 16. Anautomotive radar sensor, comprising: one or more transmitting antennas;one or more receiving antennas; a plurality of transceivers coupled tosaid one or more transmitting antennas and said one or more receivingantennas, said transceivers operative to generate and supplytransmitting signals to said one or more transmitting antennas andreceive signals reflected back to said one or more receiving antennas; aplurality of frequency sources coupled to said plurality of transceiversincluding at least a first frequency source having a first settling timeand a second frequency source having a second settling time; a controlcircuit operative to alternately couple said first frequency source andsaid second frequency source to said plurality of transceivers, therebypermitting said second frequency source to settle while said firstfrequency source is in use, and permitting said first frequency sourceto settle while said second frequency source is in use; and whereinalternating use of said first frequency source and said second frequencysource eliminates time delays associated with frequency source settlingtime in the automotive radar sensor.
 17. The apparatus according toclaim 16, wherein said first frequency source comprises a first phaselocked loop (PLL) circuit and said second frequency source comprises asecond PLL circuit.
 18. The apparatus according to claim 16, whereinsaid control circuit is operative to turn said first frequency sourceoff when transmission and reception using a first transceiver iscomplete.
 19. The apparatus according to claim 16, wherein said controlcircuit is operative to turn said second frequency source off whentransmission and reception using a second transceiver is complete.